The sorting of electronic components, such as packages that have been singulated on a mounting tape or a singulation jig, is one of the key back-end processes for the manufacture of Chip-Scale Packages (“CSP”) like Ball Grid Array (“BGA”) packages and Quad Flat No leads (“QFN”) packages.
In a CSP package, there is a lead or ball side (top surface) for making electrical connections with other devices, as well as a mold side (bottom surface) comprising an encapsulant for protecting the internal circuitry. The mold side is also commonly referred to as a marking side as labels or other information may be marked onto this surface of the package. Inspection results on the lead/ball side and mold/marking side are commonly used as sorting criteria when sorting different packages that have been formed to determine whether packages have been satisfactorily assembled. Accordingly, an important performance index for a machine used for processing semiconductor packages is its inspection and sorting throughput.
Typically, after sorting and inspecting, good packages are offloaded to a container, such as a tray or tube container, and rejected packages are disposed of in a reject bin. Further, reworked units may be transferred to yet another tray or bin.
Conventional package processing machines sort and inspect the packages individually. The packages are also picked up and transferred to the various stations as well as offloaded separately. The throughput of such processing machines is significantly lowered as a result. An example of a method to pick-up and sort singulated electronic packages individually is illustrated in U.S. Pat. No. 7,190,446 entitled “System for Processing Electronic Devices”. Singulated packages are individually picked up from a tape and placed onto holders at a certain segment of a rotary table. Concurrently, inspections of the packages take place at other segments of the rotary table. The packages are next rotated to a segment to be picked up individually by an offloading arm which transfers the packages separately to different offloading devices such as a tube, tray or bin, according to the inspection results. Pick-up and transfer of the packages are performed individually which slows down the sorting process. Furthermore, there is no flipping feature in order to expose the mold side for inspection. Inspection of the mold side of the package is done through a glass holder, which may render inspection results unreliable as a result of the quality of the glass and contamination through use.
Another pick-up and sorting apparatus is disclosed in U.S. Pat. No. 6,446,354 entitled “Handler System for Cutting a Semiconductor Package Device”. The singulated packages are picked up by a vacuum head, washed with water and dried while being held by the vacuum head. After cleaning and drying, the packages are placed onto a hot plate having an array of small vacuum holes for further drying and lead/ball surface inspection. Half of the packages are placed onto a turntable with a buffer plate on top, with pockets arranged in an alternating format. The remaining packages are put onto the second half of the buffer plate. The buffer plate rotates when required to position the packages in a preferred orientation before being picked up by dual offloading pick arms. The packages are then picked up one at a time by multiple vacuum heads on the dual offloading pick arms which transfer the packages to a position opposite the offloading device for mark inspection. The packages are further transferred to a tray or a tube according to the inspection results. This method is undesirable as a complicated pick head design using several motors to drive individual vacuum pads in the z-direction is needed. More expensive fabrication methods are required since the motor channel includes the motor itself, encoder and a driver. Additionally, while the pick-up rate of individual packages is quite fast and flexible, it is still unable to match the speed of the saw machine for producing smaller package sizes.
In yet another prior art approach, U.S. Pat. No. 6,655,045 entitled “Apparatus and Method for Pick and Place Handling” discloses a gang transfer arm which carries the singulated packages by a gang “sliding” approach. The singulated packages are slid by a rinsing carrier from a singulation jig to a rinsing platform. Next, a drying carrier moves the washed packages further for drying on the same platform. The packages are next moved in individual rows onto a transfer track and the packages are separated into separate units to be picked up individually at the end of the track. The lead/ball surface inspection can be conducted before offloading units to either a tray, tube, reject bin, or canister according to the inspection results. As different conversion kits are required for different packages, this method involves high costs. The setup and conversion are also difficult, requiring major leveling adjustments from the singulation jig to the rinsing platform, a map separator and the transfer track. Additionally, this method limits inspection to the lead/ball surface of the packages only. Furthermore, since the packages are separated into separate units to be picked up individually at the end of the track, this reduces throughput of the sorting process.
Therefore, in order to overcome the aforesaid disadvantages in the prior art, it would be desirable to provide simple and reliable apparatus and methods for handling singulated packages in groups instead of individually and which allow full inspection of multiple sides of the packages (such as their bottom and top surfaces and four side surfaces) efficiently and cost effectively.